Sewing machine belt drive



J. GALKIN SEWING MACHINE BELT DRIVE June '21, 1938.

Filed Jun 14, 1937 INVENTOR v .105 EPH GAL .K/A/

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v ATTORNEY Patented June 21, 1938 UNITED STATES PATENT OFFICE 2,121,080 SEWING MACHINE BELT DRIVE Joseph' Galkin, New York, N. Y. Application June 14, 1937, Serial No. 148,150

2 Claims.

This invention relates to a belt drive and belt tensioning mechanism to take the place of pitman drives in sewing machines and more particularly to a mechanism suitable for forming a tensioned driving connection between the main and needle-bar actuating shafts of high speed sewing machines.

An object of this invention is to provide an attachment for sewing machines having upper and lower shafts driven in timed relation, whereby a tensionable belt drive for said shafts is shielded by a housing which is integrally secured to the sewing machine frame and has a removable end cover whereby the driving mechanism may 16 be exposed to view in its entirety for tensioning the belt.

Another object of this invention is to provide in a sewing machine having upper and lower shafts driven in timed relation by a belt, a hollow overhanging enclosure for said shafts having a transversely movable belt tensioning element and a closeable opening in an end wall of said enclosure, thereby forming a repeatedly tensionable shielding belt drive adapted for high-speed sewing machines.

Another object of this invention is to provide means for moving the transverse tensioning element to cause the belt to be automatically tensioned.

With the above and other objects in view, the invention will be hereinafter more particularly described, and the combination and arrangement of parts will be shown in the accompanying drawing and pointed out in the claims which form part of this specification.

Reference will now be had to the drawing, wherein like numerals of reference designate corresponding parts throughout the several views, in which:

4 Figure 1 is a fragmentary side view of a sew- 50 frame of a sewing machine having upper and lower shafts II and I2 mounted thereon, to rotate in parallel and in timed relation to each other.

The shafts I I and I2 have been made sufliciently 55 long to extend out from the end wall I3 of the frame II) to make it possible to mount the belt driving mechanism thereon and to be entirely outside the sewing machine frame. Secured to the end wall I3 by means of screws I l and a flange I5 is a housing or casing I6 having an open end face IT. A cover plate I8 has been removably secured to the housing I6 by screws I9. As shown in Figure 1, the cover plate 58 has an opening at its upper end serving to receive the hub of the pulley on the shaft II. The cover plate I8 may 10 thus be swung about the shaft II without removing the pulley. Fixedly mounted on the shafts II and I2 are wheels, 20, 20, each having a' plurality of teeth 2I, 2I. A canvas belt 22, having transverse wire projections 23 fixed thereto and meshing with thewheel teeth 2! has been rotatably mounted on the toothed wheels 29 so as to cause the lower shaft todrive the upper shaft in timed relation.

I For the purpose of this invention, the end wall 20 or transverse support I3 of the frame It has been grooved to provide a guideway 24, positioned transverse of said frame. A slide 25, having an elongated slot 26, has been movably mounted on the guideway 24 and is secured to the frame I0 2 by a bolt 21, passing through the slot 26, and threaded in the end wall 13 of the frame II]. An idler wheel 28, having a plurality of teeth 29, similar to the teeth 2|, has been freely rotatably mounted on a stud 30, projecting at one end from 30 the slide 25, and in rotative engagement with the driving side of the belt 22;

A screw 3| has been threadably secured in a tapped. hole in one end of the slide 25, opposite the stud 30 and axially in alignment with the 35 slot 26 and perpendicular .to the bolt 21. The inner end of the screw 3| rests against a coil spring 35, which contacts the body of the bolt 21, as best shown in Figure 3. By actuating the screw 3| in the slide 25, it is possible to move the slide 25 and idler wheel 28 transversely of the frame II], as determined by the guideway 24, towards the opposite side of the belt and thus increase the tension in the belt 22. The spring 35 tends to constantly move the slide 25 and the idler wheel 28 in a transverse direction to tighten the belt 22 automatically. To permit the spring 35 to function continuously as a belt tightener, I draw up the clamping bolt 21 to less than its maximum tightened capacity, so as to leave a minute clearance between the washer 36 at the head of the bolt and the slide 25. This adjustment permits the spring 35 to move the slide 25 and the idler wheel 28 and causes the belt to be automatically tensioned.

' is lost in repairing the machine.

It is to be noted that, while I have shown the entire belt tensioning mechanism in the form of an attachment which may be secured to existing sewing machines having a hollow upright frame III, that I may install my tensioning mechanism inside the hollow frame I and provide an end opening and a cover in said frame (not shown) but similar to the end opening I! and cover I8 to the end face I3 of the sewing machine frame. It will then be possible, by removing such end cover from the frame, to tension the belt with ease and precision while the operator is fully shielded from contact with said mechanism.

In accordance with the patent statutes I have described and illustrated the preferred embodiment of my invention, but it will be understood that various changes and modifications can be made therein without departing from the spirit of the invention as defined by the appended claims.

It is to be noted that if a non-tensionable belt drive were used, that when the belt became stretched and considerably worn, it would jump over a tooth and upset the timing arrangement, with the result that the sewing machine parts become broken and considerable time and money The disclosure herein prevents such an occurrence and is a desirable advantage in the operation of sewing machines having shafts driven in timed relation.

I claim:

1. In a belt tensioning device for a sewing machine having a hollow overhanging frame including a transverse support, a casing extending longitudinally from said transverse support and. forming an enclosure for a belt, said sewing machine having a belt drive-shaft and a belt drivenshaft which extend into said casing, said casing having an open end face at a point spaced from said transverse support, said support having a transverse slideway, a slide movable on said slideway and having an elongated slot, said slide being secured to said frame by a bolt coacting with said slot, a toothed idler wheel rotatably mounted at one end of said slide, a screw means threadably positioned in said slide for adjusting said slide and idler wheel along said guideway, toothed wheels mounted on said shafts and being connected by said belt, said belt having means for engaging with said teeth to rotate said wheels in timed relation, said idler being adapted to bear against a side of said belt, a removable cover plate for the open end face of said casing, said cover plate having an opening and one of said shafts extending through said opening and permitting said cover plate to be swung about said shaft, whereby said idler wheel and said slide mechanism may be shielded or whereby it may be viewed in its entirety when tensioning said belt.

.A belt tensioning device for a sewing machine having a hollow overhanging frame which includes a transverse support, comprising a casing extending longitudinally from said transverse support and forming an enclosure for a belt, said sewing machine having a belt driveshaft and a belt driven-shaft which extend into said casing, said casing having an open end face at a point spaced from said transverse support, said support having a transverse slideway, a slide guided movably in said slideway, releasable means fixed to said transverse support and adapted to secure said slide to said frame, a toothed idler wheel rotatably mounted at one end of said slide, screw means operatively connected with said slide and coacting with said releasable means for adjusting said slide and its idler wheel along said guideway, wheels having teeth mounted on said shaft extensions, said belt having means for en gaging with said wheel teeth, said wheels being connected by said belt and being rotated in timed relation, said idler being adapted to bear against a side of said belt, a removable cover plate for the open end face of said casing, said cover plate having an opening and one of said shafts extending through said opening beyond said casing and said cover plate, said opening permitting said cover plate to be swung about one of said shafts, whereby said idler wheel and said slide mechanism may be shielded or whereby it may be viewed in its entirety when tensioning said belt.

JOSEPH GALKIN. 

